Author Topic: More noob questions (Capacitor values and SPST switches)  (Read 2174 times)

Timko

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More noob questions (Capacitor values and SPST switches)
« on: April 30, 2015, 02:03:54 PM »
I'm about to start working on my first circuit board build (instead of perfboard).  So this is the first time I'm going to aquire parts outside of a kit.

I'm working to build the 1776 Bear Hug Compressor:
http://1776effects.com/wp-content/uploads/2015/03/Bear-Hug-V2-1.pdf

Q1:  I need to buy capacitors.  The build list, on page 2 of the link above, has the following values:
47uF
10nF
10uF
10nF
100nF
4u7

I'm building a shopping cart at Small Bear, and since they have all of their capacitors in mf, I've converted them:
.047mf
.00001mf
.01mf
.0001mf
?????

I don't know what the unit is on the last value, so I'm not sure how to convert it.  Is it 4.7uF?

Q2:  The BOM calls for a SPST switch, but the vast majority of switches I see are of the 2PST variety.  I assume I can use a 2PST switch, and jump the 2 outer lugs, but is there a switch with only 2 lugs?

selfdestroyer

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Re: More noob questions (Capacitor values and SPST switches)
« Reply #1 on: April 30, 2015, 03:05:13 PM »
mF and uF are the same. Its just another way to abbreviate microfarad.

os .047mF would actually be 47nF (nanofared)

Your looking for 47mF = 47uF

Cody

Timko

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Re: More noob questions (Capacitor values and SPST switches)
« Reply #2 on: April 30, 2015, 03:28:48 PM »
Oh, that's was different than what I expected.  But that makes way more sense!

davent

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Re: More noob questions (Capacitor values and SPST switches)
« Reply #3 on: April 30, 2015, 03:30:23 PM »
Hi Timko,
Yes, 4u7  is the same as 4.7uf, just like you see resistor values written with the units in place of the decimal 4k7->4.7k.

You've correctly converted the values to millifarads which is represented by mF, but... you want microfarads, represented by F/uf, the fault is with Small Bear where they've used mF, milifarads, instead of F (or more easily typed uF), microfards, as the units.
dave

http://www.unit-conversion.info/capacitance.html

Welcome to the metric world.

« Last Edit: April 30, 2015, 04:01:18 PM by davent »
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Timko

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Re: More noob questions (Capacitor values and SPST switches)
« Reply #4 on: April 30, 2015, 03:53:00 PM »
Value      Converted Value      Capacitor Code
47uF      47uF            476   
10uF      10uF            106   
10nF      .01uF         103   
100nF   .1uF            104   
4.7uF   4.7uF         475   

Here's the chart I've come up with this.  Now when I've been looking on Smallbear, I don't see any standard ceramic or film capacitor larger than 1uF (mf).  The ones larger than 1mF are all electrolytic.  Are my assumptions correct that I need to buy film/Ceramic for the caps 3 and 4 above, and electrolytic for 1, 2, and 5?

selfdestroyer

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Re: More noob questions (Capacitor values and SPST switches)
« Reply #5 on: April 30, 2015, 04:22:40 PM »
Ok, now I am confused. Here is what Smallbear says in there Product FAQ

Quote
Help!! There so many ways of expressing capacitor values!
Capacitor values on the Stock List are Always expressed either as Microfarad (You'll see it as mf., mfd., uf., uF. in schematics and lists,) or picofarad (pf.). The use of mf. as "millifarad" is a change of recent years; it can be confusing, but the correct translation will be clear enough from how the capacitor is being used.

1000 pf. = .001 mf. = 1 nf. (nanofarad) That last is a European usage that you'll see a lot.

If you go to Home - Capacitors - Electrolytic - Aluminum Radial you will see Electrolytic, Radial 16V 1 mf - 100 mf with a product of 4.7 mF, I know for a fact that I have bought these and they are 4.7uf (4u7).

davent

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Re: More noob questions (Capacitor values and SPST switches)
« Reply #6 on: April 30, 2015, 06:25:38 PM »
According to this article, 'milli'/m was adopted as a prefix in 1795, 'micro'/ was added in 1960.

https://sites.google.com/site/largenumbers/home/2-2/2
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Re: More noob questions (Capacitor values and SPST switches)
« Reply #7 on: April 30, 2015, 08:43:44 PM »
Just to clarify, the practice of writing 4u7 (or 4k7 for resistors, for that matter) comes from the days when people wrote things down and photocopied. Later on, after the paper had aged and been handled a bit...

"Is this a decimal point, or did a fly shit on here?"

Makes it nice and crystal clear that you mean 4.7uF, not 47uF :)
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Timko

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Re: More noob questions (Capacitor values and SPST switches)
« Reply #8 on: May 01, 2015, 08:52:33 AM »
I've gotten the correct capacitors picked out then.

As far as the toggle switch:  The circuit board only have 2 solder points for it, but most of the switches have 3 connection points.  I assume that I want terminals rather than PC board mounts, and I want an on/on switch, since the switch is selecting long vs. short decay.  But how do I connect 3 terminals on the switch to the 2 connection points on the board?  I think one will probably go to ground in this case, but I wanted to check.

jimilee

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Re: More noob questions (Capacitor values and SPST switches)
« Reply #9 on: May 01, 2015, 09:00:07 AM »

I've gotten the correct capacitors picked out then.

As far as the toggle switch:  The circuit board only have 2 solder points for it, but most of the switches have 3 connection points.  I assume that I want terminals rather than PC board mounts, and I want an on/on switch, since the switch is selecting long vs. short decay.  But how do I connect 3 terminals on the switch to the 2 connection points on the board?  I think one will probably go to ground in this case, but I wanted to check.
you can either wire 2 of the lugs with 1&2 or 2&3 or find an spst switch it has 2 lugs, you're good either way though.


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Timko

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Re: More noob questions (Capacitor values and SPST switches)
« Reply #10 on: May 01, 2015, 12:38:50 PM »
Thanks for all the help!  Components have been ordered :).

jimilee

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Re: More noob questions (Capacitor values and SPST switches)
« Reply #11 on: May 01, 2015, 01:08:52 PM »

Thanks for all the help!  Components have been ordered :).
now.....we wait


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Re: More noob questions (Capacitor values and SPST switches)
« Reply #12 on: May 07, 2015, 02:19:50 AM »
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Welcome to the metric world.
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